PROJECT SUMMARY Salmonella infections are a leading cause of gastroenteritis in the US. The annual estimated burden is around 1 million cases domestically, and around 94 million cases worldwide. Prevention of Salmonella infection focuses primarily on agricultural and food preparation practices. Interestingly, salicylate analgesics such as bismuth subsalicylate (Pepto-Bismol) can be used to prevent gastroenteritis caused by Salmonella and closely related enteric pathogens. The mechanism underlying the protective effects of these drugs is not fully understood, but appear to be the result of changes in Salmonella physiology and metabolism induced by salicylates. The premise of this research is to establish a molecular mechanism between salicylate treatment and reductions in Salmonella virulence. Our emphasis is on the role of the homologous transcription factors MarA, SoxS, Rob, and RamA. All four are activated directly or indirectly by salicylate drugs. Our preliminary data show these transcription factors repress expression of key virulence genes in Salmonella. Proposed are experiments to 1) define the regulatory interactions of MarA, SoxS, Rob, and RamA with Salmonella virulence genes and 2) directly test the integrated effects of MarA, SoxS, Rob, and RamA on Salmonella adhesion and invasion of epithelial cells. These data will establish MarA, SoxS, Rob, and RamA as important inhibitors of Salmonella virulence, a class of critically understudied virulence regulators. Due to the broad conservation of MarA, SoxS, Rob, and RamA in closely related bacteria, these transcription factors may be important inhibitors of virulence traits in many other dangerous pathogens. With these findings in mind, developing compounds to specifically activate MarA, SoxS, Rob, and RamA more selectively may provide more effective drugs to prevent bacterial diarrhea.